【摘要】 文章采用密度泛函理论方法,研究少层Bi₂Se₃拓扑绝缘体薄膜的电子结构和光学性质随薄膜厚度的变化。能带结构和态密度分析发现,当薄膜厚度从5QL（quintuple layer）逐步变化到1QL时,其费米能级附近的电子态仍然保持线性色散关系;特别是当薄膜厚度减小到2QL和1QL时,由于量子限域效应,体电子态和表面电子态的能隙都明显增大,导致体电子态和表面电子态发生分离,这种分离有利于制备基于1QL和2QL的Bi₂Se₃拓扑绝缘体薄膜的自旋电子器件。光吸收系数的计算发现,厚度为5QL、4QL、3QL的薄膜在红外区有1个吸收主峰,吸收边远超出了红外区;当厚度减小到2QL和1QL时,吸收边发生明显蓝移,红外区的吸收峰蓝移且强度明显减小,这表明3QL以上的Bi₂Se₃拓扑绝缘体薄膜更适合制备红外光探测器件。更多还原

【Abstract】 The variation of the electronic structure and optical property of few-layer topological insulator Bi₂Se₃ thin film with the thickness of thin film is studied by density functional theory method.The analysis of band structures and density of states indicates that when the thickness of thin film gradually decreases from 5 QL（quintuple layer）to 1 QL,the electronic states near the Fermi level remain linear dependence of energy on momentum.Moreover,as the thickness of thin film decreases to 2 QL and1 QL,the energy gaps of both bulk electronic states and topological surface states obviously increase due to quantum confinement effect,resulting in the separation of topological surface states from bulk states.This separation is convenient to produce spintronic device based on Bi₂Se₃ thin film with the thickness of 2 QL and 1 QL.The calculated absorption coefficients show that when the thickness of thin film is 5 QL,4 QL or 3 QL,there is an absorption peak in infrared range and the absorption edge is beyond infrared range.However,when the thickness of thin film is reduced to 2 QL and 1 QL,there is an obvious blue-shift for the absorption edge and the absorption peak in infrared range weakens clearly.This suggests that the Bi₂Se₃ thin film with the thickness more than 2 QL is fit to fabricate infrared optoelectronic device.更多还原